A mesa is an isolated, flat-topped elevation, ridge or hill, which is bounded from all sides by steep escarpments and stands distinctly above a surrounding plain. Mesas characteristically consist of flat-lying soft sedimentary rocks capped by a more resistant layer or layers of harder rock, e.g. shales overlain by sandstones. The resistant layer acts as a caprock that forms the flat summit of a mesa. The caprock can consist of either sedimentary rocks such as sandstone and limestone; dissected lava flows; or a deeply eroded duricrust. Unlike plateau, whose usage does not imply horizontal layers of bedrock, e.g. Tibetan Plateau, the term mesa applies exclusively to the landforms built of flat-lying strata. Instead, flat-topped plateaus are specifically known as tablelands.
Guzhen County, which belongs to Bengbu City, Anhui Province, is located in the northeast of Anhui Province, on the north bank of the middle reaches of the Huaihe River, adjacent to the outskirts of Bengbu to the south, Tuohe River to the north and Lingbi County to the north, Wuhe County to the east, Huaiyuan County to the southwest, and Changqiao District of Suzhou to the northwest; the topography is a sloping plain, located in the transition zone between subtropical and warm temperate zones; the total land area is 1363 square kilometers. Guzhen County has a long history. Liu Bang, the ancestor of the Han Dynasty, set up Guyang County here, and the relics still exist; during the Taihe period of the Northern Wei Dynasty, Guyang Town was changed to Guyang Town, which later evolved into a solid town; in the first 202 years, the famous "Battle of Guxia" took place in Guzhen, which opened the foundation of the Han Dynasty for 400 years, leaving touching stories such as "besieged on all sides" and "Farewell my Concubine". "Guxia site" was listed as a national key cultural relic protection unit; archaeologists discovered 4.